Armature assembly



Dec. 13, 1949 R. P. SWEGER ARMATURE ASSEMBLY Filed April 11, 1945 mi{QJ/7 /0 2s 91230 /5 INVENTR. RUSSC/ P. Sanger' ATTURNEYS Patented Dec.13, 1949 ARMATURE ASSEMBLY Russell I. Sweger, Rockford, Ill., assignorto Barber-Colman Company, Rockford, Ill., a corporation of IllinoisApplication April 11, 1945, Serial No. 587,662

(Cl. 20G-87) 3 Claims.

The present invention pertains to armature assemblies for relays or likedevices.

Generally stated, the object of the present invention is to provide anarmature assembly for relays or like `devices which is of such characterthat temperature changes within a wide range will not adversely aifectits operating characteristics.

Further objects and advantages will become apparent as the Afollowingdescription proceeds, taken in connection with the accompanying drawingsin which:

Figure 1 is a side elevation of a relay equipped with an armatureassembly embodying the present invention, the casing being shown insection.

Fig. 2 is an enlarged sectional view taken substantially along the line2--2 in Fig. 1.

Fig. 3 is a sectional View taken substantially along the line 3-3 inFig. 2.

Fig. 4 is an exploded :perspective view of the armature assembly.

Fig. 5 is van exploded perspective view of a modied armature assemblyalso embodying the present invention and, like the assembly of Fig. 4,adapted for use in the relay shown in Figs. 1 to 3.

Referring more particularly to the exemplification of the inventionillustrated in the drawings, the invention has been shown as embodied inan armature assembly designated generally as I0. This particularassembly happens to -have been designed for use in the polarized relayshown in Figs. l to 3. The relay shown is simply an example of one ofthe many forms of devices in which armature assemblies embodying thepresent invention may be used; and this particular relay as a whole is,with the exception of the novel armature assembly here underconsideration, disclosed and claimed in the copending application ofClark V. Bullen and Carl J. Anderson, Serial No. 487,244, led May 17,1943, which issued as Patent 2,443,784 on June 22, 1948. It will beunderstood therefore that there is no intention to limit the presentinvention to such an installation nor to details inessential to practiceof the invention, even though a preferred embodiment is described andshown in some detail. On the contrary, `the intention is to cover al1uses, modifications, alterations and alternative constructions fallingwithin the spirit and scope of the invention as expressed in theappended claims.

In the particular relay shown, the stator, designated generally as II,comprises a pair of blockshaped permanent magnets I2 made of Alnico orother material having a high degree of magnetic retentivity. The magnetsare spanned by upper and lower bridges I4, I5, being xed in place bythrough-fasteners IAB. Inturned from the opposite side edges of each ofthe bridges I4, I5 are integral ears constituting pairs of opposed polepieces I8, I9 and 20, 2I. The air gaps between the ends of therespective pairs of pole pieces are aligned with each other on thetransverse center line of the stator structure. The pole `pieces arepermanently Imafgnetized by the magnets I2. The upper pole pieces I8, 20may. for example, be north poles and the lower pole pieces south poles.

Encircling the transverse center line of the stator II passing throughthe air gaps between the two .pairs of ypole pieces is an actuatingwinding 22. If an armature, a specific example of which is describedbelow, is positioned t0 extend axially through such winding,energization of the latter will tend to rock the armature about itscenter. Flow of current through the winding in one direction will causethe armature to rock in one direction, while flow of current in theopposite direction will correspondingly cause the armature to rock in anopposite direction. Contacts may thus be controllably opened or closedin accordance with the direction of current flow through the actuatingwinding.

Polarized relays of the general type described above are extremelysensitive instruments. They are intended to respond when a very feeblecurrent is applied to the actuating winding. For precision results itis, moreover, necessary that any drift or change in the so-calledcontrol point should be eliminated. In other words, the value of thecurrent to which the relay responds should not be subject to inadvertentchange during use of the instrument.

Factors which contribute to change in the control point are numerous.They have been difficult to segregate both because they arise from avariety of causes and because of the minute character of the aberrationsin operation which are involved. The present invention is based in largemeasure on my discovery that the more or less necessary use of twometals in an armature assembly for such a device is likely to result inwhat seems to be a thermally induced bowing of the bimetal structure andwhich, in any event, manifests itself in the operation of the relay as ashift in control point. Normally the armature assembly must include anarmature made of ferromagnetic material in order that it may perform itsmagnetic circuit functions. Likewise, a second member is normallysecured to the armature and made of a different metal either to afford adesired high degree of electrical conductivity to ac,

commodate the same for use as a contact support or a desired springinessfor movably supporting the armature, or both. Actual measurement of anythermally induced bowing of such a bimetallic structure, resulting fromthe dissimilar thermal expansion characteristics of the two metals whichcomprise it, must usually be done by microscope because of the minutecharacter of the movement which takes place. My own conclusion ordeduction is that such warpage does take place and is responsible forthe shift in control point upon change in temperature, the latter shiftbeing a denitely detectable physical phenomenon. That deduction israther conclusively a'rmed by my discovery that when the armatureassembly is constructed in accordance with the present invention tocompensate mechanically for any such: tendency to warp, control pointshift as an incident to temperature change is obviated.

In the armature assembly I illustrated herein isy included an armature23 consisting of a thin plate'lilie wafer of soit iron or other suitableferromagnetic material. It is. generally rectangular in form, beingdimensioned to extend into the air gaps between botho the opposed pairsof pole pieces I8, I9 and 23,. 21|. The central portion of the armatureis of reduced cross-section so that it; will readily become saturated inthe event of application of excessive current to the actuating. winding22. For that purpose a central aperture 24 and side notches 25 arefashioned in the armature.

To the top face of the armature 23, and in face-r to-face contact withit, is' secured a carrier 2li in' the form of a one-piece resilientsheet metalstamping. Suchy stamping is made of electrically conductivebut non-magnetic material, preferably beryllium copper. Thin andtorsional-ly flexible lateral projections 26aaife preferably' providedin the` stamping 25 to extend from the central portion of the latter asshown (Fig. 4) and serve to permit rocking of the: armature aboutl itstrans- Verse central axis during operation of the relay.

The projections 23a are bent downward and their outer ends terminate inelongated supportfv ing elements or bridges 231iy which' are clampedbetween the opposed' endA faces of the pole pieces (Fig. 2). Alsoconstitutinga part of the stamp-` ing 26 are elongated and oppositelyextending cantilever contact fingers 23C. To the outer endsV of thesengers are xed contact poi-nts 2l posi'-V tioned for coractionr withstationary contact points 2B carried on adjusting screw-s' 23, supportedby brackets 33 fixed to outer sides of the lower polie' pieces |19, 2|.

The dissimilarity in metals used in theV arma^-- ture assembly elements23 and 256* described above,v and occasioned by their respectivediierent functions, results in. a structure consisting of two metalparts secured' together in faceto-f`ace con--V tact and which havewidely divergent thermal ex pansion characteristics. With such arrange=ment asv that so far described it has beenfou-nd that the relay displaysa shift in control point incident Y to temperature` change. Whatapeparently happens is that thel loi-'metall structure' 23; 231 warps moreor less in the manner of a bimeta-l'- thermostat blade when subjected totemperatureA change, resulting a variation inspacing loe-- tween theends of the armature and the stator pole pieces, or variation in1contactspacing, orv both.

Pursuant. tol the presentj inventiom the diiicuilty outlinedv above is4overcome byV fixing' to: the tace ci thev armature: 223 opposite thattov which isf at-I tached the sheet metal stamping 26 a second sheetmetal stamping which is adapted to inhibit or prevent the bowing whichwould otherwise occur. In the present instance a stamping 3| which isapproximately of a diamond shape is fixed to the underside of thearmature 23.

The stamping 3| is fixed to the armature 23 by the same pair of rivets32 which secure the carrier stamping 23 in place, so that the points ofattachment of the two sheet metal members to the armature match.Moreover, such points of attachment are preferably located symmetricallywith respect to both the longitudinal and transverse axes of thearmature.

In order that the two sheet metal stampings 26, 3| shall prevent theapplication or development of bending forces on the armature, the twoshould have substantially the same coecient of thermal expansion. Thatis most simply achieved b-y fashioning them both from the samematerial'. Moreover, the two sheet metal faces should developapproximately the same strength, that is` toA say, have approximatelythe same resistance to compression or tension, between the points ofriveting. For that purpose they may be made of metal of the same gaugeand shaped as. shown to ailc-rd cross-sections of substantially the samemean area.

With the added stamping 3| secured tothe underside of the armature asdescribed above, shift in control point for the relay, incident tochange in temperature, is substantially eliminated Vsof far as thearmature is concerned.

The assembly and operation of the relay shown:

will in general be clear from the foregoing. By y wayv of briefrecapitulation, it may be noted that the parts are arranged as.illustrated the contacts adj-usted for a desired clearance'. Forcesapplied to the armature 23 by the permanent.l magnet flux may be readilybalanced by adjusting shunts 33. In the illustrated arrangement such:magneticl shunts' are shown as being four in number, two being pivotedyon each of. the upper' pole pieces I8,l 2t. These stripsare offerromagnetic material and are resiliently urged into contactthe: outerfaces. of adjacent ones of the permarient magnets EL By shitting theshunts magnetic: potential across the corresponding an? gaps may becorrespondingly varied. toE bri-ng; the armature into magnetic: balance,

Hav-ing assembled and adjusted the relay as1 noted above, they same isoperated by applying energizingl current to the actuating winding 22,-Ar current flowing in onef direction will cause the armature 23- to rockcounterclockwise (as viewed in Eig.. 21) therebyv closing; theleftl'iand.I pair' of' contact points 21;, 23'. Similarly.r currentowing in. the opposite direction throughv the winding 2?;l will rock thearmature clockwise to close thel other orrighthand-f pair of contacts21,21%.` Upon deenergization of the actuating winding the. tor;sifonally stressed carrier projections 26a. restorel the armature to itsmidi positionl and in which bothf sets` ofi contacts are open.

By reason of the temperature compensating arrangement', includingspecifically the added stamping 3|? described above, the'instruini-:ni'fs control point remains substantially unchanged evenIthough: the armature be subjected to widely varying temperatures; Theprecisionof the n-e strument-isthus effectually protected againstifmpairm'ent byV change inarmature temperature:

In Fig. 5y is shown a modiied' armatureassembly-v al'so' embodying thepresent invention?. In this' ze instance two layers o'iron'- with one ofberyllium copper sandwiched between has been used, rather than thereverse arrangement previously described in which a layer of iron issandwiched between two of conductive sheet metal.

In the particular construction shown in Fig. 5 a pair of duplicateferromagnetic armature sections 40 are used. Each is of the same shapeas the armature 23 heretofore described although each section may be ofonly approximately half the thickness of the single piece armature 23.Between the sections 40 is sandwiched a sheet metal carrier 26 similarin construction to that previously described, but with the supportingelements 26b formed as separate stampings. The

carrier and the armature parts are secured together by a pair of rivets32 as before. With such an arrangement thermally induced bowing of thearmature is electually prevented for the reasons mentioned previously.

I claim as my invention:

1. In an armature assembly for a relay or the like, the combinationcomprising a plate-like ferromagnetic armature member and a sheet metalcontact supporting member disposed in face-toiace relation and havingdissimilar thermal exfr' pansion characteristics, pivot means for saidarmature having a pivoting axis lying parallel to the plane thereof, athird member made of the same 'material as one of said nist-mentionedmembers,

together with means for rigidly securing all three of said memberstogether in stacked relation with the two members of like materialhaving the remaining member sandwiched therebetween, and the resistanceto bending of the two members of like material being substantially equalso that there is no tendency for a point on said armature remote fromsaid pivoting axis to rotate about said axis upon subjecting saidassembly to a change in temperature.

2. In an armature assembly for a relay or the like, the combination oi aplate-like ferromagnetic armature, a contact support including anonmagnetic electrically conductive portion of sheet metal overlying oneface of said armature and having a contact supporting finger integraltherewith and projecting outward from the armature, a second portion ofsheet metal of the same material as the rst-mentioned one overlying theopposite face of said armature, means for rigidly securing said portionsof sheet metal to the respective opposite faces of said armature at aplurality of points matched in position for each of said portions ofsheet metal, the resistance to lateral bending of each of said portionsof sheet metal between their respective points of attachment to saidarmature being substantially equal.

3. In an armature assembly for a relay or the like, the combination of aplate-like ferromagnetic armature, a Contact support including anon-magnetic electrically conductive portion of sheet metal overlyingone face of said armature and having a pair of contact supporting ngersintegral therewith and projecting outward from the armature at oppositeends of the latter in alignment with each other, means adapting saidarmature for pivotal mounting about a central axis parallel to the planeof said armature and perpendicular to the longitudinal axis of saidcontact supporting ngers, a second portion of sheet metal of the samematerial and thickness as the iirst one overlying the opposite face ofsaid armature, and a plurality of rivets passed through said armaturerigidly securing said portions of sheet metal to the latters oppositefaces at matched points spaced on the armature in a directionlongitudinal of said fingers equi-distant from the pivotal axis thereof.

RUSSELL P. SWEGER.

REFERENCES CITED The following references are of record in the ille ofthis patent:

UNITED STATES PATENTS Number Name Date 1,254,380 Brinton Jan. 29, 19182,020,106 Crago Nov. 5, 1935 2,143,097 Warnke Jan. 10, 1939 2,240,576Pye May 6, 1941 2,351,377 Warsher June 13, 1944 2,357,834 Leifer et alSept. 12, 1944 2,443,784 Bullen et al June 22, 1948

